Final answer:
True, unconjugated bilirubin is converted to conjugated bilirubin in the liver with the help of the enzyme UDP-glucuronyl transferase, which enhances its solubility for excretion.
Step-by-step explanation:
True, in the liver, unconjugated bilirubin is converted to conjugated bilirubin via the enzyme UDP-glucuronyl transferase. When bilirubin arrives at the liver, it is in its unconjugated, water-insoluble form. With the help of the enzyme UDP-glucuronyl transferase, unconjugated bilirubin undergoes a process where it is linked (conjugated) to glucuronic acid, which results in conjugated bilirubin. This process occurs in two steps, first to form bilirubin monoglucuronide, and then bilirubin diglucuronide. This conversion enhances the solubility of bilirubin, allowing it to be more easily excreted in bile and then into the intestine. In conditions such as Crigler-Najjar syndrome and Gilbert's disease, UDP-glucuronyl transferase activity is reduced or absent, leading to elevated levels of unconjugated bilirubin in the blood.